Protective coated article



Aug 20, 1940- H. l.. KOHLER A 2,212,269

PROTECTIVE COATED ARTICLE Filed Nov. 9, 1938 ZINC COAT/N6 6 SHEET .STEELZ /N C -MERCUR AMALGAM COA TlNG ZINC CAT/NGV ZINC C OA TING i Z/Nc -MERCURY AMALGAM COAT/NG INVENTOR HENRY l.. KOHLER BY ATTORNEY Patented Aug.20, 1940 UNITED STATES PATENT OFFICE Andrew A. Kramer,

Kansas City, Mo.

Application November 9, 1938, Serial No. 239,670

6 Claims.

My invention relates to protective coated articles, and moreparticularly to sheet metal articles provided with a protective coating.This application is a continuation in part of my copending aplicationSerial No. 144,029, filed May 21, 1937, patented March 21, 1939, PatentNo. 2,150,929.

A diculty that has always existed in the utilization of galvanizedmetallic sheets for making certain articles out of the same, has beenthat the galvanizing coating is not sufficiently resistant to corrosionunder certain conditions to make the practical use thereof possible. Anattempt to overcome this diiiculty has been made by providing a heaviergalvanizing coating on the sheet. The heavy zinc coating thus provided,however, has the disadvantage that, when the sheet is bent, the coatingat the bend would crack and tend to peel or flake oil". As a result,although the.' sheet as a whole was provided with a heavy galvanizingcoating' over its er1-tire surface before being fabricated, the bendingof a sheet to form a flange or a seam thereon, frequently damaged thegalvanizing coating on the sheet so seriously that it would render thecoat.- ing partially ineffective, on the Outside of the bends requiredto form the anges, or seams. Consequently the advantage of the heavygalvanizing coating on the sheet was largely lost, this being truebecause, at the point at which the galvanizing coating was caused to bedamaged, or ruptured, by bending, the sheet would be, for practicalpurposes, no better than an uncoated sheet, as far as resistance tooxidization, `or other corrosion, was-concerned. While many attemptshave been made to overcome this diculty, by a hot dipping process afterthe article has been formed from the galvanized sheet, for example, thisis diflicult to accomplish and requires expensive equipment, if anylarge sheet metal article is to be galvanized after fabrication by sucha dipping process.

It is a purpose of my invention to provide means for overcoming theabove mentioned difculty with galvanized sheets having a heavy coatingof zinc thereon, and at the same time to provide a sheet that is moreresistant to corrosion over the entire area thereof, if this is desired,than is possible with ordinary zinc coatings provided by a galvanizingprocess. I accomplish this by providing a mercury-zinc amalgam coatingon the sheet, which is applied y to any area thereof that may bedesired.

My improved protective coating may be utilized 5g to give betterprotection than zinc against certain types of corrosion, or corrosiondue to certain causes, either over the entire area of a metallic sheet,or over the entire area of one side thereof, or over the entire area ofa fabricated sheet metal section, or one side of such 5 a section, ifthis should be desired,` and is particularly adapted for use at andadjacent the bends in a fabricated sheet, whereby any rupture in thegalvanizing coating that may have occurred during fabrication, from anyof the 10 fabrication steps, will be closed and the sheet protected atsuch bends, or other fabricated p0rltions thereof, more effectively thanwas the case before the bending, or other operation, thereon, thatdamaged, or ruptured, the protective zinc coating on the sheetoriginally.

It is a further purpose of my invention to provide a protectivev coatingof a zinc-mercury amalgam that has the same appearance as the zinccoating originally on the sheet as obtained 20 by the galvanizingprocess. Galvanized metallic sheets have a characteristic Spangledappearance.

It is highly desirable to maintain this Spangled appearance of the sheetafter my improved coating has been plac'ed thereon. This is accom- 25plished by utilizing a paste-like zinc-mercury amalgam, which is appliedto the sheet in a manner that the structural characteristics of the zinccoating on the sheet are not changed. My improved protective coatingwill resist every 30 kind of corrosion equally as well, as does thegalvanized sheet before having the treatment `ythereof, whereby myimproved coating is produced, and for most uses, will produce acoatingthat will be more resistant to corrosion than the 35 heavy galvanizingcoating applied to such sheets, or fabricated sheet metal sections. Asthe term fabrication is used herein, it means any bending, cutting orpunching operation, or any other operation on a sheet, that may beperformed 40 thereon after the same has been rolled and galvanized.

Other objects and advantages of my invention will appear as thedescription of the same proceeds. I desire to have'it understood,however, 45 that I do not intend to limit myseif to the particulardetails` described, except as defined in the claims.

In the drawing:

Fig. 1 is a fragmentary sectional view on a greatly enlarged scale,showing my improved amalgam coating applied to a sheet having a bendtherein, and

Fig. 2 is a similar view, showing my improved 55 amalgam coating appliedto av sheet otherwise fabricated than by bending.

Referring in detail tothe drawing, in Figs. 1 and 2 the metallic bodyportion of the sheet, which is usually steel or iron, is indicated bythe numeral 3. The sheet shown in Fig. 1 is bent at 4 and the bend maycause damage to the zinc coating ordinarily on the galvanized sheet onthe outer side of the bend substantially at the outer corner thereof.The zinc coatingprovided on the sheet is indicated by the numeral 5 andthe amalgam coating around the outside of the bend and adjacent saidbend in the sheet is indicated in Fig. 1 by the numeral 6. i

In Fig. 2 the same numerals are applied to the zinc coating and theamalgam coating, but instead of showing a sheet'with a bend therein, thesheet is shown as being fabricated by punching a hole 1 therein, thisbeing merely illustrative of some fabrication operation that may beperformed on the sheet that may damage the ordinary zinc galvanizingcoating thereon.

My improved protective coating is provided on galvanized sheets thathave been fabricated to the desired size and shape, by bending,die-shaping, cutting and'punching operations, or any of these that' maybe necessary to produce the article, or sections of an article, of thedesired shape from the galvanized sheet of metal. After the sheet hasbeen fabricated, it is cleaned at the places at which the protectivecoating is to be provided thereon, usually by means of dilutehydrochloric acid, or a solution of tin chloride, or antimony chloride,or lead chloride, or zinc chloride, or cyanide of soda. This cleaningsolution may be applied with a brush or swab of some character, and theexcess may be removed with a cloth,

' or any other suitable means. When it is desired to apply theprotective coating only at or adjacent a ruptured area on a galvanizedsheet, or an area that may have been damaged to the extenty ofinjuringthe protective coating, or rupturing the same, the galvanizedsheets are cleaned only on the outer sides of all bends therein, or anyother area at which the coating may have been ruptured, or damaged, andareas adjacent these bends, or other areas where the damage may haveoccurred. A zone at the place at which the rupture in the zinc coatingmay exist will thus be cleaned, and also a zone on each side thereof.

A putty-like amalgam of mercury and zinc is made up prior to cleaningthe sheets, or is made up in quantity to be used whenever necessary,said amalgam having such proportions of zinc and mercury therein as toproduce a soft putty-like material of the consistency of thick paste orcream. 'I'he proportions of zinc and mercury that are used to producethis soft putty-like material will vary somewhat, dependent upon theatmospheric temperature existing, as the material must, of course, be ofthe soft, creamy putty-like character at the temperature at which it isapplied to the sheet. Thus in the winter time, when a lower temperatureis encountered, both in the atmosphere and in the material of the sheetsthemselves, a larger proportion of the mercury to the zinc must be usedto produce this soft putty-like coating material. I have found that 15%zinc and mercury by weight will produce an amalgam of the desiredconsistency in the summer time, while in the winter time, when thetemperatures are exceedingly low, it is necessary to utilize an amalgammade for this purpose that will have as little as 10% zinc by weight,and mercury by weight, while, if the mercury is heated while the zinc isbeing incorporated therein, the percentage of zinc can be increased to20% by weight to 80% by weight of mercury. The relative proportions ofthe metal, or metals, amalgamating with mercury that have to be utilizeddepend upon the melting points of the metals that are amalgamated withmercury and the temperature encountered, and the heating makes itpossible to incorporate a larger amount of the metal amalgamating withthe mercury, than would otherwise be the case. There is no advantage inincorporating too large a percentage of zinc in the amalgam, however, asit must, of course, remain of a creamy character, or a puttylikecharacter, at the temperature at which it is applied to the sheet, andif too large a percentage of zinc is included in the amalgam by addingthe zinc to the heated mercury, it will not have the desired consistencyat the temperature at which it is to be utilized.

The zinc can be in the form of any small particles, such as shavings,yturnings, cuttings, or in the form of a powder or granules. The nelydivided zinc is stirred into the quantity of mercury that is to beutilized to make the amalgam in the proportions necessary, substantiallywithin the limits above referred to. This is ordinarily done withoutheating the mercury, but the mer' cury may be heated to incorporate asomewhat larger percentage of zinc in the amalgam than would otherwisebe possible within the limits pointed out above. Care must, of course,be utilized in doing this, that the mercury is not heated to atemperature near the vaporization point thereof.

The soft putty-like amalgam of zinc and mercury, produced as abovedescribed, is applied to the cleaned zone, or area, of the galvanizedsheet, by a brushing or rubbing operation, the soft puttylike amalgambeing brushed or rubbed onto the cleaned area of the sheet with a cloth,or in a similar manner. This rubbing or brushing operation spreads thezinc-mercury amalgam over the cleaned area of the sheet and causes athin layer thereof to adhere to the outer surface of the zinc coating onthe sheet. In case there is a rupture or a damaged area in the sheet,from which the zinc has been entirely, or substantially entirely,removed, the zinc-mercury amalgam will adhere to the sheet at thisruptured area also. 'Ihe amalgam, as soon as it contacts the zinccoating on the sheet, begins to act thereon to amalgamate the zinc onthe sheet with some of the mercury in the amalgam. Due to the brushingof the amalgam back and forth over the ruptured area, the compositionofthe coating atthe ruptured area will tend to be substantially the sameas on other portions of the sheet to which the amalgam is applied. Anyloose flakes, or particles, of zinc will be dissolved in the amalgam,amalgamating with the mercury in said amalgam.

The action between the zinc-mercury amalgam and the zinc on the sheetwill continue until the amalgam has penetrated the entire zinc coatingof the sheet, at least down to the ferrous zinc alloy at the surface ofthe iron or steel of the sheet. After the zinc on the sheet amalgamateswith the mercury, the resulting amalgam will gradually become stifferand harder, as the greater the amount of other metal amalgamated withthe mercury the harder and stiffer the amalgam will become. As a result,the penetration of the zinc on the sheet by the zinc-mercury amalgam,will eventually produce a zinc-mercuryr amalgam throughout the coatingon the sheet,

which will have lost the soft character that the zinc-mercury. amalgamhad when applied and will become as hard as the zinc coating originallyon the sheet.

Thus,. while the amalgam, when first placed on the sheet, will be softenough that it can be rubbed off on the fingers to a certain extent,after at least twenty-four hours, the coatingat the area to which theamalgam has been applied will be hard enough that none of the same Willrub olf and the sheet can be handled without any damage to the coatingthereon, just as readily as was the case with the zinc coating on thesheet originally. The sheet will, after the coating has become hard,have substantially the sameappearance as it did before any amalgam wasapplied thereto, and none of. the coating can be rubbed oiT, even thoughit may be rubbed persistently for a considerable period of time. Thecoating will have the characteristic Spangledl appearance of the zinccoatingoriginally on the sheet. This indicates that the application ofthe putty-like amalgam to the sheet that has been previously galvanized,while resulting in the dissolving of the zinc on the sheet, in themercury of the amalgam, does this in such a gradual manner that theliquefactionof the coating material on the sheet takes place at such aslow rate through the thickness of the zinc coating, that the structureof 'the zinc coating on the sheet is not altered, ,although thecomposition changes from substantially pure zinc to a zinc-mercuryamalgam, as the amalgamating process proceeds through the coating. Thesheet will accordingly have substantially the same appearance two or`three days after the amalgam was applied thereto as it had before anyAapplication of amalgam thereto.

It is obvious that it may be desirable to not only prevent corrosion atruptures in coatings on galvanized sheets at bends in such sheets', orsimilar places, but that the entire area of a sheet,

` or the entire inner surface of a sheet, or section of a container, forexample, that is innermost when it is in place, and which is subjectedto the corrosive action of sulphuric acid, or other compounds, which areordinarily found in oil tanks, or similar receptacles, may be providedWith a corrosion resisting amalgam coating. By utilizing my protectivecoating, the corrosive action, caused by these sulphur compounds, on thezinc coating of the sheet ordinarily occurring will be reduced andsubstantially eliminated, the zincmercury amalgam being applied to theinner surface of such oil tank, or the sections of such an oil tank;made up of sheets lthat have been bent, cut and punched before theapplication of the amalgam thereto.

The tendency of the sulphur compounds, when acting on the amalgamcoating described, is to cause the mercury in the amalgam to formaprotective film on the surface that vis exposed to the action ofthedilute sulphuric acid, or hydrogen sulphide, or other sulphur compounds,this causing some slight loss of some of the zinc, but the mercuryarresting this substantially immediately,`

due to its nlm forming action.

While it is immaterial whether `the amalgam which it was -applied atrst, this being on the top surface of the coating. However, if theamalgam above referred 'to is left in contact with the zinc coating fortwenty-four hours or more', and an excessive amount of the amalgam isnot used, suflicient of the mercury will amalgamate with the zinc thatall of the zinc will become' amalg'amated with the mercury, and theresulting coating will be a zinc-mercury amalgam from the outer surfaceof the coating to at least the ferrous zinc alloy at the surface of themetal of the sheet. The amalgamation of the mercury with the zinc on thesheet, when completed, causes the coating to have a hard character,because there is so much larger apercentage'of zinc in the coating, thanthere Was in the amalgam applied to the sheet, and the coating will have'a hard character, similar to that Vof the zinc, instead of a softputty-like character, such as the zinc-mercury amalgam, that was appliedto the amalgam resulting will contain .approximately zinc and 10%mercury. With heavier coatings of zinc, the percentage of zinc will, ofcourse, be higher. `Thus zinc coatings as thick as two and one-halfounces per running square foot,-

have been utilized on galvanized sheets, and for such coatings theresulting amalgam on the sheet will contain about 95,6% zinc, and 4.4%mercury. The putty-like amalgam is applied only thick enough tocompletely coat the sheet and, of course, with a heavier zinc coatingthe -resulting amalgam would contain a much smaller percentagev ofmercury than where sheets with lighter coatings of zinc are treated toproduce my improved amalgam coating. As some variation can also bepracticedin the vpercentages,

of zinc or mercury in the putty-like amalgam, depending upon temperatureconditions, it has been found that the amount of zinc can b'e variedbetween 10% and 20% and said putty-like coating materials produced forapplication to the sheet to produce the amalgam that eventually isformed on said sheet. Due to these variations,

the percentage of zinc finally on the sheet where the amalgam coating isprovided thereon will range between 89% and 96%, while the percentagelof mercury will rangebetwee'n 11% and 4%. In all cases, the amalgamresulting that is on the sheet will contain well over 50% zinc and thecoating will not lose the characteristics of a zinc coating, except inpart, but will be modified to some extent in its characteristics by themercury contained therein, the mercury acting to make the coating moreresistant to corrosion'than the zinc coating was originally. Such a zincmercury amalgam coating on a sheet is particularly desirable where it ispreferred that no lead, or tin, or other metal than zinc and mercury, bepresent on the surface of the sheet. While the zinc will tend todissolve under the same circumstances in which it would dissolve on anordi- .nary galvanized sheet, in a sheet that is provided with anamalgam coating, such as described herein, the mercury in the-amalgamacts to arrest this action on the zinc and causes the zinc-mercuryamalgam coating to have a much longer life than a pure zinc coatingwould have.

Itis highly desirable that the Spangled appearnsA A ance of the coatingon the sheet, such as it has when galvanized, be maintained, as thiscoating has a desirable appearance from the standpoint of the user, anddue to the familiarity of the user with the spangled appearance ofgalvanized sheets, any destruction of this appearance is found to beobjectionable from a commercial standpoint.

What I claim is:

1. A galvanized sheet having a coating of zinc and mercury containingfrom eight to sixteen parts of zinc to one part of mercury by weight onone side thereof, said coating having at least as great a proportion ofmercury at its exposed surface as adjacent the metal of the sheet.

2. A galvanized sheet having a bend therein l and having a coating ofzinc and mercury containing from eight to sixteen parts of zinc to one'`part of mercury by Weight on the side thereof 4. A galvanized sheethaving a bend therein and having a mercury-zinc amalgam coating on theinside thereof lying on the outside of said bend at and adjacent saidbend, said coating having at least as great a proportion of mercury atits exposed surface as adjacent the metal of the sheet and having a muchgreater proportion of zinc than mercury therein.

5. A fabricated steel sheet having a zinc galvanizing coating therein,said zinc coating having interruptions therein, and a zinc-mercuryamalgam coating thereon over and adjacent the interruptions in said.zinc coating, said amalgam coating having at least as great a proportionof mercury at its exposed surface as adjacent the metal of the sheet andhaving a much greater proportion of zinc than mercury therein.

6. A galvanized metallic sheet having a zinc coatingon a portion of theareathereof and a coating of an amalgam composed of zinc and mercury onthe remainder of the area thereof, said amalgam coating having at leastas great a proportion of mercury at its exposed surface as adjacent thevmetal of the sheet and having a much greater proportion of zinc thanmercury therein.

HENRY L. KOHLER.

